DESCRIPTION: The experiments in this proposal are designed to test a model of early selective attention. Selective attention subserves the function of visual exploration early in development. Selective attention is hypothesized in the model to be the product of a balance between suppression and disengagement. Suppression allows prolonged fixation and sustained attention when necessary, and disengagement allows attentional switching when necessary. Based on prior research these two processes are hypothesized to be imbalanced during the early postnatal months in favor of suppression. This results in prolonged fixations, inadequate visual sampling through saccadic eye movements, and difficulties disengaging attention. Development in the model consists of regulating the balance between suppression and disengagement. The balance model is tied to neurophysiology by postulating that the superior colliculus is the site of the fixation/suppression signals and the parietal cortex is the site of the disengagement signals. A signal detection approach is used to incorporate the effects of noise and to make quantitative ordinal predictions from this balance model of selective attention. The experiments test various predictions from this model. Infants at ages 6-, 14-, and 24-weeks of age will participate in these experiments. This research will contribute to our knowledge of how visual selective attention develops early in life. As such, it is potentially relevant to understanding disorders of attention later in development.